Filament buffer

ABSTRACT

A machine for manufacturing additive printed parts includes a first filament cartridge adapted to support a length of filament of a material from which the additive printed parts will be manufactured, a print head moveably supported within the machine, and a first filament buffer positioned between the first filament cartridge and the print head and including a first buffer volume. The filament supported within the first filament cartridge extends from the first filament cartridge, through the first filament buffer, and to the print head and is allowed to deflect within the first buffer volume.

INTRODUCTION

The present disclosure relates to machines that create additive printedparts and more particularly to a filament buffer for a machine thatcreates additive printed parts.

Machines for manufacturing additive printed parts generally include aprint head that includes a feed motor to pull a filament of polymermaterial to the print head. The filament of polymer material isgenerally provided as a coiled spool that is contained remotely from theprint head. The feed motor must pull with enough force to rotate thespool, unwind filament from the coil, and pull the filament to the printhead. This force can be large depending on the type of filament and howbig the coil of filament is. It is desirable to make the print head ofsuch a machine as small as possible, thus, while current known machinesachieve their intended purpose, there is a need for a new and improvedmachine for manufacturing additive printed parts where the forcenecessary to pull the polymer filament into the print head is minimized.

SUMMARY

According to several aspects of the present disclosure, a machine formanufacturing additive printed parts includes a first filament cartridgeadapted to support a length of filament of a material from which theadditive printed parts will be manufactured, a print head moveablysupported within the machine, and a first filament buffer positionedbetween the first filament cartridge and the print head and including afirst buffer volume. The filament supported within the first filamentcartridge extends from the first filament cartridge, through the firstfilament buffer, and to the print head. The first buffer volume adaptedto allow the filament passing through the first filament buffer todeflect.

In one aspect, the print head includes an extruder and a nozzle. Theextruder is adapted to pull the filament from the first filament bufferinto the print head and feed the filament into the nozzle.

In another aspect, the machine further includes a first feed motormounted within and integral to the first filament buffer, positionedbetween the first filament cartridge and the first buffer volume. Thefirst feed motor pulls the filament from the first filament cartridgeand feeds it into the first buffer volume.

In another aspect, the first filament buffer includes a first openingand a second opening. Filament extending from the first filamentcartridge enters the first filament buffer through the first opening andexits the first filament buffer through the second opening.

In another aspect, the first buffer volume is positioned between thefirst and second openings of the first filament buffer and includes afirst sidewall and a second side wall, wherein the filament can deflecttwo-dimensionally between the first and second side walls.

In another aspect, the first side wall extends substantially linearlybetween the first and second openings and the second side wall extendsbetween the first and second openings and includes a shape that allowsthe filament to deflect in the direction of the second side wall awayfrom the first side wall. As the filament extends through the firstbuffer volume of the first filament buffer the filament deflectstwo-dimensionally between a first position, wherein the filament extendsalong a substantially linear path between the first and second openingsadjacent the first side wall, and a second position, wherein thefilament extends along a curved path between the first and secondopenings adjacent the second side wall.

In another aspect, the distance traveled by the filament between thefirst and second openings when the filament is adjacent the first sidewall is shorter than the distance travelled by the filament between thefirst and second openings when the filament is adjacent the second sidewall, wherein when the filament is deflected toward the second side wallthere is slack in the filament within the buffer volume such that theforce necessary to pull the filament into the print head by the extruderis not affected by any resistance applied to the filament up-stream ofthe buffer volume.

In another aspect, the machine further includes a first sensor and asecond sensor mounted within the first filament buffer. The first sensordetects the presence of the filament within the first buffer volume whenthe filament is positioned adjacent the first side wall within the firstbuffer volume. The second sensor detects the presence of the filamentwithin the first buffer volume when the filament is positioned adjacentthe second side wall within the first buffer volume.

In another aspect, the machine further includes a spool rotatablymounted within the first filament cartridge that supports a coiledlength of filament and is freely rotatable to allow filament to un-windfrom the coil and to be pulled from the first filament cartridge.

In another aspect, the machine further includes a second filamentcartridge, substantially identical to the first filament cartridge andadapted to support a length of the filament, a second feed motor mountedwithin and integral to the first filament buffer and positioned betweenthe second filament cartridge and the first buffer volume, and afilament intersection positioned between the first and second feedmotors and the first buffer volume of the first filament buffer. Thefilament intersection directs the filament extending, alternatively,from either the first or second filament cartridges into the firstbuffer volume of the first filament buffer.

In another aspect, the machine further includes a second filamentcartridge, substantially identical to the first filament cartridge andadapted to support a length of the filament, and a second filamentbuffer positioned between the second filament cartridge and the printhead and having a second buffer volume; wherein the filament supportedwithin the second filament cartridge extends from the second filamentcartridge, through the second filament buffer, and to the print head,and the second buffer volumes is adapted to allow the filament passingthrough the second filament buffer to deflect.

In another aspect, the machine further includes a second feed motormounted within and integral to the second filament buffer and positionedbetween the second filament cartridge and the second buffer volume,wherein the filament supported within the second filament cartridge ispulled from the second filament cartridge and is fed into the secondbuffer volume by the second feed motor.

In another aspect, the second filament buffer includes a first openingand a second opening, wherein the filament extending from the secondfilament cartridge enters the second filament buffer through the firstopening of the second filament buffer and exits the second filamentbuffer through the second opening of the second filament buffer.

In another aspect, the machine further includes a filament intersectionpositioned between the first and second filament buffers and the printhead, wherein the filament intersection is adapted to direct thefilament extending, alternatively, from either the first or secondfilament buffers to the print head.

In another aspect, the second buffer volume is positioned between thefirst and second openings of the second filament buffer and includes afirst sidewall and a second side wall. The filament passing through thesecond buffer volume can deflect two-dimensionally between the first andsecond side walls of the second buffer volume.

In another aspect, the first side wall of the second buffer volumeextends substantially linearly between the first and second openings ofthe second filament buffer and the second side wall of the second buffervolume extends between the first and second openings of the secondfilament buffer and is shaped to allow the filament to deflecttwo-dimensionally between a first position, wherein the filament extendsalong a substantially linear path between the first and second openingsof the second filament buffer adjacent the first side wall of the secondbuffer volume, and a second position, wherein the filament extends alonga curved path between the first and second openings of the secondfilament buffer adjacent the second side wall of the second buffervolume.

In another aspect, the distance traveled by the filament between thefirst and second openings of the second filament buffer when thefilament is adjacent the first side wall of the second buffer volume isshorter than the distance travelled by the filament between the firstand second openings of the second filament buffer when the filament isadjacent the second side wall of the second buffer volume, wherein whenthe filament is deflected toward the second side wall of the secondbuffer volume there is slack in the filament within the second buffervolume such that the force necessary to pull the filament into the printhead by the extruder is not affected by any resistance applied to thefilament up-stream of the second buffer volume.

In another aspect, the machine further includes a first sensor and asecond sensor mounted within the second filament buffer to detect thepresence of the filament within the second buffer volume when thefilament is positioned adjacent the first side wall within the secondbuffer volume and the second sensor is adapted to detect the presence ofthe filament within the second buffer volume when the filament ispositioned adjacent the second side wall within the second buffervolume.

In another aspect, the machine further includes a spool rotatablymounted within the second filament cartridge and adapted to support acoiled length of the filament and to rotate freely to allow filament toun-wind from the coil and to be pulled from the second filamentcartridge.

According to several aspects of the present disclosure, a machine formanufacturing additive printed parts includes a plurality of filamentcartridges, a print head moveably supported within the machine, and aplurality of filament buffers. Each of the plurality of filamentcartridges includes a spool rotatably mounted therein, wherein the spoolwithin each of the plurality of filament cartridges supports a coiledlength of filament of a material from which the additive printed partswill be manufactured and rotates freely to allow the filament to un-windfrom the coil and to be pulled from the filament cartridge. The printhead has an extruder and a nozzle mounted within the print head, whereinthe extruder pulls the filament from the plurality of filamentcartridges into the print head and feeds the filament into the nozzle.Each of the plurality of filament buffers is positioned between one ofthe plurality of filament cartridges and the print head, and includes afirst opening, a second opening, a buffer volume positioned between thefirst and second openings, and a feed motor. The filament is pulled froma one of the plurality of filament cartridges and fed into the firstopening of each of the filament buffers by the feed motor within each ofthe plurality of filament buffers, extends through the buffer volume ofeach of the filament buffers, is allowed to deflect within the buffervolume of each of the plurality of filament buffers as the filamentpasses through each of the plurality of filament buffers, exits each ofthe filament buffers through the second opening of each of the pluralityof filament buffers and extends from each of the filament buffers to theprint head.

In another aspect, the buffer volume of each of the plurality offilament buffers includes a first sidewall extending substantiallylinearly between the first and second openings and a second side wallextending between the first and second openings having a shape thatallows the filament to deflect in the direction of the second side wallaway from the first side wall, wherein as the filament extends throughthe buffer volume of each of the plurality of filament buffers thefilament deflects two-dimensionally between a first position, whereinthe filament extends along a substantially linear path between the firstand second openings adjacent the first side wall, and a second position,wherein the filament extends along a curved path between the first andsecond openings adjacent the second side wall.

In another aspect, within each of the plurality of filament buffers, thedistance traveled by the filament between the first and second openingswhen the filament is adjacent the first side wall is shorter than thedistance travelled by the filament between the first and second openingswhen the filament is adjacent the second side wall, wherein when thefilament is deflected toward the second side wall there is slack in thefilament within the buffer volume such that the force necessary to pullthe filament into the print head by the extruder is not affected by anyresistance applied to the filament up-stream of the buffer volume.

In another aspect, each of the plurality of filament buffers includes afirst sensor mounted adjacent the first side wall and a second sensormounted adjacent the second side wall, wherein the first sensor isadapted to detect the presence of the filament when the filament is inclose proximity to the first side wall and the second sensor is adaptedto detect the presence of the filament when the filament is in closeproximity to the second side wall.

According to several aspects of the present disclosure, a filamentbuffer for additive printed part manufacturing includes a first openingand a second opening, wherein a filament of building material for anadditive printed part is fed into the filament buffer through the firstopening and exits the filament buffer through the second opening, and abuffer volume is positioned between the first and second openings toprovide a space into which the filament can deflect.

In another aspect, the filament buffer further includes a feed motoradapted to pull the filament into the filament buffer and feed thefilament into the buffer volume.

In another aspect, the buffer volume is positioned between the first andsecond openings and includes a first sidewall and a second side wall,wherein the filament can deflect two-dimensionally between the first andsecond side walls.

In another aspect, the first side wall extends substantially linearlybetween the first and second openings and the second side wall extendsbetween the first and second openings and includes a deep curved shapethat allows the filament to deflect in the direction of the second sidewall, such that as the filament extends through the buffer volume thefilament deflects two-dimensionally between a first position, whereinthe filament extends along a substantially linear path between the firstand second openings adjacent the first side wall, and a second position,wherein the filament extends along a curved path between the first andsecond openings adjacent the second side wall.

In another aspect, the distance traveled by the filament between thefirst and second openings when the filament is adjacent the first sidewall is shorter than the distance travelled by the filament between thefirst and second openings when the filament is adjacent the second sidewall, wherein when the filament is deflected toward the second side wallthere is slack in the filament within the buffer volume such that theforce necessary to pull the filament out of the filament buffer throughthe second opening is not affected by any resistance applied to thefilament up-stream of the buffer volume.

In another aspect, the filament buffer further includes first and secondsensors mounted therein, the first sensor being adapted to detect thepresence of the filament when the filament is adjacent the first sidewall and the second sensor adapted to detect the presence of thefilament when the filament is adjacent the second side wall.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a perspective view of a machine for manufacturing additiveprinted parts according to an exemplary embodiment;

FIG. 2 is a perspective view of a print head for the machine accordingto an exemplary embodiment;

FIG. 3 is a perspective view of a spool and coil of filament for themachine according to an exemplary embodiment;

FIG. 4 is an internal view of a filament cartridge for the machineaccording to an exemplary embodiment;

FIG. 5 is a perspective view of a filament buffer for the machineaccording to an exemplary embodiment;

FIG. 6A is an exploded view of the buffer body, cover, and feed motorfor a filament buffer according to an exemplary embodiment;

FIG. 6B is an exploded view of the buffer body, cover, and feed motorsfor a filament buffer according to an exemplary embodiment;

FIG. 6C is an exploded view of two filament buffers in a stackedarrangement;

FIG. 7 is a cross sectional view as indicated by arrows 7-7 in FIG. 6A;

FIG. 8 is a cross sectional view as indicated by arrows 8-8 in FIG. 6A;

FIG. 9 is a perspective view of a machine for manufacturing additiveprinted parts according to an exemplary embodiment;

FIG. 10A is a schematic view of a machine for manufacturing additiveprinted parts according to an exemplary embodiment having one filamentcartridge and one filament buffer;

FIG. 10B is a schematic view of a machine for manufacturing additiveprinted parts according to an exemplary embodiment having two filamentcartridges and one filament buffer; and

FIG. 10C is a schematic view of a machine for manufacturing additiveprinted parts according to an exemplary embodiment having two filamentcartridges and two filament buffers.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses.

Referring to FIG. 1, a machine for manufacturing additive printed partsfrom a polymer material is shown generally at 10. The machine 10includes a housing 12 within which components of the machine 10 aresupported. The machine 10 includes a print head 14, a first filamentcartridge 40, and a first filament buffer 50. The first filament buffer50 is positioned between the first filament cartridge 40 and the printhead 14. A filament 26 extends from the first filament cartridge 40passes through the first filament buffer 50 and then on to the printhead 14.

Referring to FIG. 2, the print head is shown generally at 14. The printhead 14 is moveable two-dimensionally in a horizontal plane along anx-axis 16 and a y-axis 18 within the housing 12 and includes an extruder20 and a nozzle 22. The extruder 20 includes a print head feed motor 24and is adapted to pull the filament 26 into the print head 14. Theextruder 20 then feeds the filament 26 to the nozzle 22. The nozzle 22includes a heater 28 that melts the filament 26 as it enters the nozzle22. The nozzle 22 also includes a tip 30 adapted to feed molten filamentmaterial out of the nozzle 22 to be deposited when an additive printedpart is being created. Continual feeding of the filament 26 into thenozzle 22 by the extruder 20 pushes the molten filament material throughthe tip 30 of the nozzle 22 to be deposited.

Referring again to FIG. 1, a build table 32 is supported below the printhead 14 and is vertically movable up and down along a z-axis 34. Thebuild table 32 also includes a print bed 36. The print bed 36 provides asurface onto which an additive printed part is created within themachine 10. When the machine 10 is used to create an additive printedpart, the build table 32 starts out positioned high within the machine10 near the print head 14. The print head 14 moves back and forth twodimensionally along the x-axis 16 and y-axis 18 depositing moltenpolymer material onto the print bed 36 and creating a two-dimensionalshape on the print bed 36. Once fed from the tip 30 of the nozzle 22 themolten filament material quickly hardens sufficiently to hold shape. Thebuild table 32 gradually moves downward along the z-axis 34 away fromthe print head 14 as successive layers of molten material are depositedon previously deposited layers of hardened material. The print head 14continues to add successive layers onto the forming additive printedpart until a final three-dimensional shape is formed.

The machine 10 can create additive printed parts from different kinds ofmaterial. In an exemplary embodiment the filament 26 is made from apolymer material. The filament 26 can have varying size, color andmaterial composition. The filament 26 that the machine 10 uses comescoiled onto a spool 38, as shown in FIG. 3. Referring to FIGS. 1 and 4,the first filament cartridge 40 supports the spool 38 of filament 26 sothe filament 26 can be fed into the machine 10 to the print head 14. Thespool 38 is rotatably supported within the first filament cartridge 40.FIG. 4 shows the interior of the first filament cartridge 40 with anempty spool 38 supported therein. The first filament cartridge 40includes an opening 42 formed therein to allow the filament 26 to extendout of the first filament cartridge 40. The spool 38 is supportedco-axially on a hub 44. The hub 44 is rotatably supported to allow boththe hub 44 and the spool 38 supported on the hub 44 to rotate about acenter axis 46. Preferably, the hub 44 is supported within the firstfilament cartridge in a manner that allows the hub 44 and spool 38 tofreely rotate. In the first filament cartridge 40 shown in FIG. 4, thehub 44 is supported within the first filament cartridge by a bearing 48.Free rotation of the hub 44 within the first filament cartridge 40 isimportant to ensure the filament 26 can easily unwind from the spool andminimize the amount of force necessary to pull the filament 26 from thefirst filament cartridge 40.

In order to minimize mass and optimize packaging, it is desirable thatthe print head 14 be as small as possible. The extruder 20 within theprint head 14 pulls the filament 26 from the first filament cartridge 40into the print head 14 and feeds the filament 26 to the nozzle 22.Because the print head 14 must be small, the extruder 20 is alsorelatively small. In general, the force necessary to rotate the spool 38and unwind the coil of filament 26 is on the order of ten times theforce that the extruder 20 pulls the filament into the print head 14.Therefore, it is desirable to minimize the force necessary to pull thefilament 26 into the print head 14.

Referring to FIG. 1, a first filament buffer 50 is positioned betweenthe first filament cartridge 40 and the print head 14. Filament 26extending from the first filament cartridge 40 passes through the firstfilament buffer 50 and then on to the print head 14. Referring to FIGS.5, 6A, 7 & 8, the first filament buffer 50 includes a cover 52 and afirst buffer body 54. The cover 52 of the first filament buffer 50 isadapted to be attached to the first buffer body 54 and has a cover face56 that mates to the first buffer body 54. The first buffer body 54includes a cavity 56 formed therein. The cavity 56 is defined by a firstside wall 58, a second side wall 60, and a bottom wall 62 formed withinthe first buffer body 54. When the cover 52 is attached to the firstbuffer body 54, the first sidewall 58, the second side wall 60, thebottom wall 62 and the cover face 56 define a first buffer volume 64.The first buffer volume 64 allows the filament 26 passing through thefirst filament buffer 50 to deflect. Deflection of the filament 26within the first filament buffer 50 creates slack in the length offilament 26 between the first filament cartridge 40 and the print head14.

The first filament buffer includes a first opening 66 formed at a firstdistal end 68 and a second opening 70 formed at a second distal end 72.The filament 26 from the first filament cartridge 40 enters the firstfilament buffer 50 through the first opening 66 and exits the firstfilament buffer 50 through the second opening 70 to extend onward to theprint head 14. The first buffer volume 64 is positioned between thefirst and second openings 66, 70 of the first filament buffer 50. FIG.10A is a schematic representation of the path the filament 26 takes asit is pulled from the first filament cartridge 40 by the first feedmotor 78 and fed through the first filament buffer 50 and finally to theprint head 14

The first side wall 58 extends substantially linearly between the firstand second openings 66, 70. The second side wall 60 extends between thefirst and second openings 66, 70 and includes a concave curved shapethat allows the filament 26 to deflect in the direction of the secondside wall 60 away from the first side wall 58. The exact shape of thesecond side wall 60 is similar to a tear drop. Beginning near the firstopening 66 the second side wall 60 slopes sharply away from the firstside wall 58. At a point where the width of the first buffer volume 64between first and second side walls 58, 60 is largest, the second sidewall turns back toward the first side wall 58 and gradually moves closerto the first side wall 58 as the second side wall 60 extends to thesecond opening 70 within the first filament buffer 50. The shape of thesecond side wall 60 is similar to the shape to which the filament 26will naturally deflect. This shape is important to ensure the filament26 can easily deflect within the buffer volume 64 and that the filament26 will move smoothly through the first buffer volume 64.

As the filament 26 extends through the first buffer volume 64 thefilament 26 deflects two-dimensionally between a first position 74 and asecond position 76. In the first position 74, the filament 26 extendsalong a substantially linear path between the first and second openings66, 70 adjacent the first side wall 58. In the second position 76, thefilament 26 extends along a curved path between the first and secondopenings 66, 70 adjacent the second side wall 60.

When the filament 26 deflects to the second position 76, there is slackin the filament 26, adding to the length of filament 26 within the firstbuffer volume 64. The distance traveled by the filament 26 between thefirst and second openings 66, 70 when the filament 26 is adjacent thefirst side wall 58 is shorter than the distance travelled by thefilament 26 between the first and second openings 66, 70 when thefilament 26 is adjacent the second side wall 60. When the extruder 20within the print head 14 pulls the filament 26 into the print head 14,the extruder 20 must pull with enough force to overcome all frictionalresistance acting on the filament 26 upstream of the extruder 20. Thiscan be particularly problematic if the spool 38 of coiled filament 26 isvery large. The extruder 20 within the print head 14 must pull withenough force to rotate the spool 38 and un-wind the filament 26 from thecoil. If the force is too much, the extruder 20 may not be able to pullwith enough force to overcome frictional resistance. If this happens,the machine 10 will stop functioning. Alternatively, if the resistanceis too much, the print head feed motor 24 within the extruder 20 maystrip the surface of the filament 26 causing slippage in the extruder20. Either instance results in a disruption in the operation of themachine 10.

If the filament 26 is deflected away from the first side wall 58 towardthe second position 76, adjacent the second side wall 60 within thefirst buffer volume 64, there is slack in the filament 26 within thefirst buffer volume 64. This slack provides a free length of filament 26within the first buffer volume 64 that can be pulled from the firstbuffer volume 64 with little resistance. When the filament 26 isdeflected away from the first side wall 58 and there is slack in thefilament 26 within the first buffer volume 64, the force necessary topull the filament 26 into the extruder 20 within the print head 14 isnot affected by any frictional resistance applied to the filament 26up-stream of the first buffer volume 64.

A first feed motor 78 is mounted within and integral to the firstfilament buffer 50. The first buffer body 54 includes a cavity 80 withinwhich the first feed motor 78 is positioned, and the cover 52 is shapedto provide a housing 82 for the first feed motor 78 when the cover 52 isattached to the first buffer body 54. The first feed motor 78 pulls thefilament 26 from the first filament cartridge 40 and into the firstopening 66. The first feed motor 78 also pushes the filament 26 into thefirst buffer volume 64.

The first feed motor 78 pulls the filament 26 from the first filamentcartridge 40 and pushes the filament 26 into the first buffer volume 64faster than the extruder 20 pulls the filament 26 from the firstfilament buffer 50. Because the filament 26 is coming into the firstbuffer volume 64 faster than the filament 26 is exiting the first buffervolume 64, the filament 26 is forced to deflect within the first buffervolume 64.

The first buffer body 54 includes two sensor pockets 84, 86. A firstsensor pocket 84 is formed within the first side wall 58 of the firstbuffer volume 64 and a second sensor pocket 86 is formed within thesecond side wall 60 of the first buffer volume 64. The sensor pockets84, 86 are adapted to support first and second sensors 88, 90 to detectthe presence of the filament 26. The sensors 88, 90 can be mechanical,wherein the sensors 88, 90 include a mechanical switch 92 extending intothe first buffer volume 64 that is triggered when the filament 26 comesinto physical contact with the mechanical switch 92. Alternatively, thesensors 88, 90 can be optical sensors that are triggered when thefilament 26 is near the sensors 88, 90.

The sensors 88, 90 provide feedback to allow proper control of themachine 10. The machine 10 runs optimally when the filament 26 extendingthrough the first filament buffer 50 is deflected within the firstbuffer volume 64. Deflection is accomplished due to the first feed motor78 pushing the filament 26 into the first buffer volume 64 faster thanthe filament 26 is being pulled from the first filament buffer 50. Thesensors 88, 90 detect the presence of the filament 26 within the firstbuffer volume 64 and provide that information to the controls of themachine 10.

If the filament 26 extending through the first filament buffer 50 is notdeflected within the first buffer volume 64, the first sensor 88 willdetect the filament 26 adjacent the first side wall 58. If the firstsensor 88 detects the presence of the filament 26, the first feed motor78 is turned on. The first feed motor 78 feeds filament 26 into thefirst buffer volume 64 faster than the filament 26 is being pulled fromthe first buffer volume 64 causing the filament 26 to deflect. When thefilament 26 has fully deflected within the first buffer volume 64, thefilament 26 will trigger the second sensor 90. When the second sensor 90is triggered, the first feed motor 78 is turned off. As the machinecontinues to operate, the extruder 20 in the print head 14 pullsfilament 26 from the first filament buffer 64, taking up the slack inthe filament 26 and causing less deflection of the filament 26. When allslack in the filament 26 is gone, the filament 26 is no longer deflectedand is adjacent the first side wall 58. When the first sensor 88 onceagain detects that the filament 26 is adjacent the first side wall 58,the first feed motor 78 is once again turned on. This cycle is repeatedas the machine 10 operates. With feedback from the first and secondsensors 88, 90, the first feed motor 78 cycles on and off as necessaryto maintain deflection of the filament 26 within the first buffer volume64.

Referring to FIG. 9, in another aspect of the present disclosure, amachine for manufacturing additive printed parts from a polymer materialis shown generally at 110. The machine 110 includes a housing 120 withinwhich components of the machine 110 are supported. The machine 110includes a print head 114 that is moveable two-dimensionally in ahorizontal plane along an x-axis 116 and a y-axis 118 within the housing112.

Referring to FIG. 2, The print head is shown generally at 114. The printhead 114 includes an extruder 120 and a nozzle 122. The extruder 120includes a print head feed motor 124 and is adapted to pull a filamentof polymer material 126 into the print head 114. The extruder 120 thenfeeds the filament 126 to the nozzle 122. The nozzle 122 includes aheater 128 that melts the filament 126 as it enters the nozzle 122. Thenozzle 122 also includes a tip 130 adapted to feed molten polymermaterial out of the nozzle 122 to be deposited when an additive printedpart is being created. Continual feeding of the filament 126 into thenozzle 122 by the extruder 120 pushes the molten polymer materialthrough the tip 130 of the nozzle 122 to be deposited.

Referring again to FIG. 9, a build table 132 is supported below theprint head 114 and is vertically movable up and down along a z-axis 134.The build table 132 also includes a print bed 136. The print bed 136provides a surface onto which an additive printed part is created withinthe machine 110. When the machine 110 is used to create an additiveprinted part, the build table 132 starts out positioned high within themachine 110 near the print head 114. The print head 114 moves back andforth two dimensionally along the x-axis 116 and y-axis 118 depositingmolten polymer material onto the print bed 136 and creating atwo-dimensional shape on the print bed 136. Once fed from the tip 130 ofthe nozzle 122 the molten polymer material quickly hardens sufficientlyto hold shape. The build table 132 gradually moves downward along thez-axis 134 away from the print head 114 as successive layers of moltenmaterial are deposited on previously deposited layers of hardenedpolymer material. The print head 114 continues to add successive layersonto the forming additive printed part until a final three-dimensionalshape is formed.

The machine 110 can create additive printed parts from different kindsof polymer material. The filament 126 can have varying size, color andmaterial composition. The filament 126 that the machine 110 uses comescoiled onto a spool 138, as shown in FIG. 3. Referring to FIGS. 9 and 4,a first filament cartridge 140 supports a spool 138 of filament 126 sothe filament 126 can be fed into the machine 110 to the print head 114.A second filament cartridge 141, identical to the first filamentcartridge 140, supports an identical spool 138 of filament 126 so thefilament 126 can be fed into the machine 110 to the print head 114. Thespools 138 are rotatably supported within the first and second filamentcartridges 140, 141. FIG. 4 shows the interior of the first and secondfilament cartridges 140, 141 with an empty spool 138 supported therein.The first and second filament cartridges 140, 141 each include anopening 142 formed therein to allow the filament 126 to extend out. Thespool 138 is supported co-axially on a hub 144. The hub 144 is rotatablysupported to allow both the hub 144 and the spool 138 supported on thehub 144 to rotate about a center axis 146. Preferably, the hub 144 issupported in a manner that allows the hub 144 and spool 138 to freelyrotate. In the first and second filament cartridges 140, 141 as shown inFIG. 4, the hub 144 is supported within the each of the first and secondfilament cartridges 140, 141 by a bearing 148. Free rotation of the hub144 within each of the first and second filament cartridges 140, 141 isimportant to ensure the filament 126 can easily unwind from the spool138 and minimize the amount of force necessary to pull the filament 126from the first and second filament cartridges 140, 141.

In order to minimize mass and optimize packaging, it is desirable thatthe print head 114 be as small as possible. The extruder 120 within theprint head 114 pulls the filament 126 from the first filament cartridge140 into the print head 114 and feeds the filament 126 to the nozzle122. Because the print head 114 must be small, the extruder 120 is alsorelatively small. Therefore, it is desirable to minimize the forcenecessary to pull the filament 126 into the print head 114.

Referring to FIG. 9, a first filament buffer 150 is positioned betweenthe first and second filament cartridges 140, 141 and the print head114. Filament 126 extending from the first and second filamentcartridges 140, 141 passes through the first filament buffer 150 andthen on to the print head 114. Referring to FIGS. 5, 6B, 7 & 8, thefirst filament buffer 150 includes a cover 152 and a first buffer body154. The cover 152 of the first filament buffer 150 is adapted to beattached to the first buffer body 154 and has a cover face 156 thatmates to the first buffer body 154. The first buffer body 154 includes acavity 156 formed therein. The cavity 156 is defined by a first sidewall 158, a second side wall 160, and a bottom wall 162 formed withinthe first buffer body 154. When the cover 152 is attached to the firstbuffer body 154, the first sidewall 158, the second side wall 160, thebottom wall 162 and the cover face 156 define a first buffer volume 164.The first buffer volume 164 allows the filament 126 passing through thefirst filament buffer 150 to deflect. Deflection of the filament 126within the first filament buffer 150 creates slack in the length offilament 126 between the first and second filament cartridges 140, 141and the print head 114.

The first filament buffer 150 includes a first opening 166 formed at afirst distal end 168 and a second opening 170 formed at a second distalend 172. The filament 126 from the first and second filament cartridges140, 141 enters the first filament buffer 150 through the first opening166 and exits the first filament buffer 150 through the second opening170 to extend onward to the print head 114. The first buffer volume 164is positioned between the first and second openings 166, 170 of thefirst filament buffer 150.

The first side wall 158 extends substantially linearly between the firstand second openings 166, 170. The second side wall 160 extends betweenthe first and second openings 166, 170 and includes a concave curvedshape that allows the filament 126 to deflect in the direction of thesecond side wall 160 away from the first side wall 158. As the filament126 extends through the first buffer volume 164 the filament 126deflects two-dimensionally between a first position 174 and a secondposition 176. In the first position 174, the filament 126 extends alonga substantially linear path between the first and second openings 166,170 adjacent the first side wall 158. In the second position 176, thefilament 126 extends along a curved path between the first and secondopenings 166, 170 adjacent the second side wall 160.

When the filament 126 deflects to the second position 176, there isslack in the filament 126, adding to the length of filament 126 withinthe first buffer volume 164. The distance traveled by the filament 126between the first and second openings 166, 170 when the filament 126 isadjacent the first side wall 158 is shorter than the distance travelledby the filament 126 between the first and second openings 166, 170 whenthe filament 126 is adjacent the second side wall 160. When the extruder120 within the print head 114 pulls the filament 126 into the print head114, the extruder 120 must pull with enough force to overcome allfrictional resistance acting on the filament 126 upstream of theextruder 120. This can be particularly problematic if the spool 138 ofcoiled filament 126 is very large. The extruder 120 within the printhead 114 must pull with enough force to rotate the spool 138 and un-windthe filament 126 from the coil. If the force is too much, the extruder120 may not be able to pull with enough force to overcome frictionalresistance. If this happens, the machine 110 will stop functioning.Alternatively, if the resistance is too much, the print head feed motor124 within the extruder 120 may strip the surface of the filament 126causing slippage in the extruder 120. Either instance results in adisruption in the operation of the machine 110.

If the filament 126 is deflected away from the first side wall 158toward the second position 176, adjacent the second side wall 160 withinthe first buffer volume 164, there is slack in the filament 126 withinthe first buffer volume 164. This slack provides a free length offilament 126 within the first buffer volume 164 that can be pulled fromthe first buffer volume 164 with little resistance. When the filament126 is deflected away from the first side wall 158 and there is slack inthe filament 126 within the first buffer volume 164, the force necessaryto pull the filament 126 into the extruder 120 within the print head 114is not affected by any frictional resistance applied to the filament 126up-stream of the first buffer volume 164.

A first feed motor 178 and a second feed motor 179 are mounted withinand integral to the first filament buffer 150. The first buffer body 154includes a cavity 180 within which the first and second feed motors 178,179 are positioned, and the cover 152 is formed to provide a housing 182for the first and second feed motors 178, 179 when the cover 152 isattached to the first buffer body 154. A filament intersection 194 ispositioned between the first and second feed motors 178, 179 and thefirst buffer volume 164. The first feed motor 178 pulls filament 126from the first filament cartridge 140 and feeds the filament 126 to thefilament intersection 194. The second feed motor 179 pulls filament 126from the second filament cartridge 141 and feeds the filament 126 to thefilament intersection 194. FIG. 10B is a schematic representation of thepath the filament 126 takes through the machine 110.

The filament intersection 194 is adapted to alternatively allow filament126 from the first and second filament cartridges 140, 141 to be fedinto the first buffer volume 164 of the first filament buffer 150. Thefilament intersection 194 allows the filament 126 to be pulled fromeither the first filament cartridge 140 or the second filament cartridge141. This provides the ability to have more or different filamentreadily available to the machine 110. When the filament 126 from thefirst filament cartridge 140 runs out, the filament intersection 194 canallow filament 126 from the second filament cartridge 140 to be fed intothe first filament buffer 150 with minimal interruption to the machine110.

The feed motors 178, 179 pull the filament 126 from the filamentcartridges 140, 141 and push the filament 126 into the first buffervolume 164 faster than the extruder 120 pulls the filament 126 from thefirst filament buffer 150. Because the filament 126 is coming into thefirst buffer volume 164 faster than the filament 126 is exiting thefirst buffer volume 164, the filament 126 is forced to deflect withinthe first buffer volume 164.

The first buffer body 154 includes two sensor pockets 184, 186. A firstsensor pocket 184 is formed within the first side wall 158 of the firstbuffer volume 164 and a second sensor pocket 186 is formed within thesecond side wall 160 of the first buffer volume 164. The sensor pockets184, 186 are adapted to support first and second sensors 188, 190 todetect the presence of the filament 126. The sensors 188, 190 can bemechanical, wherein the sensors 188, 190 include a mechanical switch 192extending into the first buffer volume 164 that is triggered when thefilament 126 comes into physical contact with the mechanical switch 192.Alternatively, the sensors 188, 190 can be optical sensors that aretriggered when the filament 126 is in close proximity to the sensors188, 190.

The sensors 188, 190 provide feedback to allow proper control of themachine 110. The machine 110 runs optimally when the filament 126extending through the first filament buffer 150 is deflected within thefirst buffer volume 164. Deflection is accomplished due to the firstfeed motor 178 pushing the filament 126 into the first buffer volume 164faster than the filament 126 is being pulled from the first filamentbuffer 150. The sensors 188, 190 detect the presence of the filament 126within the first buffer volume 164 and provide that information to thecontrols of the machine 110.

If the filament 126 extending through the first filament buffer 150 isnot deflected within the first buffer volume 164, the first sensor 188will detect the filament 126 adjacent the first side wall 158. If thefirst sensor 188 detects the presence of the filament 126, the first orsecond feed motor 178, 179 is turned on. The first or second feed motor178, 179 feeds filament 26 into the first buffer volume 164 faster thanthe filament 126 is being pulled from the first buffer volume 164causing the filament 126 to deflect. When the filament 126 has fullydeflected within the first buffer volume 164, the filament 126 willtrigger the second sensor 190. When the second sensor 190 is triggered,the first or second feed motor 178, 179 is turned off. As the machinecontinues to operate, the extruder 120 in the print head 114 pullsfilament 126 from the first filament buffer 164, taking up the slack inthe filament 126 and causing less deflection of the filament 126. Whenall slack in the filament 126 is gone, the filament 126 is no longerdeflected and is adjacent the first side wall 158. When the first sensor188 once again detects that the filament 126 is adjacent the first sidewall 158, the first or second feed motor 178, 179 is once again turnedon. This cycle is repeated as the machine 110 operates. With feedbackfrom the first and second sensors 188, 190, the first or second feedmotor 178, 179 cycles on and off as necessary to maintain deflection ofthe filament 126 within the first buffer volume 164.

Referring again to FIG. 9, in another aspect of the present disclosure,a machine for manufacturing additive printed parts from a polymermaterial is shown generally at 210. The machine 210 includes a housing212 within which components of the machine 210 are supported. Themachine 210 includes a print head 214 that is moveable two-dimensionallyin a horizontal plane along an x-axis 216 and a y-axis 218 within thehousing 212.

Referring to FIG. 2, The print head is shown generally at 214. The printhead 214 includes an extruder 220 and a nozzle 222. The extruder 220includes a print head feed motor 224 and is adapted to pull a filamentof polymer material 226 into the print head 214. The extruder 220 thenfeeds the filament 226 to the nozzle 222. The nozzle 222 includes aheater 228 that melts the filament 226 as it enters the nozzle 222. Thenozzle 222 also includes a tip 230 adapted to feed molten polymermaterial out of the nozzle 222 to be deposited when an additive printedpart is being created. Continual feeding of the filament 226 into thenozzle 222 by the extruder 220 pushes the molten polymer materialthrough the tip 230 of the nozzle 222 to be deposited.

Referring again to FIG. 9, a build table 232 is supported below theprint head 214 and is vertically movable up and down along a z-axis 234.The build table 232 also includes a print bed 236. The print bed 236provides a surface onto which an additive printed part is created withinthe machine 210. When the machine 210 is used to create an additiveprinted part, the build table 232 starts out positioned high within themachine 210 near the print head 214. The print head 214 moves back andforth two dimensionally along the x-axis 216 and y-axis 218 depositingmolten polymer material onto the print bed 236 and creating atwo-dimensional shape on the print bed 236. Once fed from the tip 230 ofthe nozzle 222 the molten polymer material quickly hardens sufficientlyto hold shape. The build table 232 gradually moves downward along thez-axis 234 away from the print head 214 as successive layers of moltenmaterial are deposited on previously deposited layers of hardenedpolymer material. The print head 214 continues to add successive layersonto the forming additive printed part until a final three-dimensionalshape is formed.

The machine 210 can create additive printed parts from different kindsof polymer material. The filament 226 can have varying size, color andmaterial composition. The filament 226 that the machine 210 uses comescoiled onto a spool 238, as shown in FIG. 3. Referring to FIGS. 9 and 4,a first filament cartridge 240 supports a spool 238 of filament 226 sothe filament 226 can be fed into the machine 210 to the print head 214.A second filament cartridge 241, identical to the first filamentcartridge 240, supports an identical spool 238 of filament 226 so thefilament 226 can be fed into the machine 210 to the print head 214. Thespools 238 are rotatably supported within the first and second filamentcartridges 240, 241. FIG. 4 shows the interior of the first and secondfilament cartridges 240, 241 with an empty spool 238 supported therein.The first and second filament cartridges 240, 241 each include anopening 242 formed therein to allow the filament 226 to extend out. Thespool 238 is supported co-axially on a hub 244. The hub 244 is rotatablysupported to allow both the hub 244 and the spool 238 supported on thehub 244 to rotate about a center axis 246. Preferably, the hub 244 issupported in a manner that allows the hub 244 and spool 238 to freelyrotate. In the first and second filament cartridges 240, 241 as shown inFIG. 4, the hub 244 is supported within the each of the first and secondfilament cartridges 240, 241 by a bearing 248. Free rotation of the hub244 within each of the first and second filament cartridges 240, 241 isimportant to ensure the filament 226 can easily unwind from the spool238 and minimize the amount of force necessary to pull the filament 226from the first and second filament cartridges 240, 241.

In order to minimize mass and optimize packaging, it is desirable thatthe print head 214 be as small as possible. The extruder 220 within theprint head 214 pulls the filament 226 from the first and second filamentcartridges 240, 241 into the print head 214 and feeds the filament 226to the nozzle 222. Because the print head 214 must be small, theextruder 220 is also relatively small. Therefore, it is desirable tominimize the force necessary to pull the filament 226 into the printhead 214.

A first filament buffer 250 is positioned between the first filamentcartridge 240 and the print head 214. A second filament buffer 251,substantially identical to the first filament buffer 250, is positionedbetween the second filament cartridge 241 and the print head 214.Filament 226 extending from the first filament cartridge 240 passesthrough the first filament buffer 250 and then on to the print head 214.Filament 226 extending from the second filament cartridge 241 passesthrough the second filament buffer 251 and then on to the print head214.

The first filament buffer has a first buffer body 254 and the secondfilament buffer 251 has a second buffer body 255. The first and secondfilament buffers 250, 251 are adapted to be stacked on one another. Acover 252 is mounted onto the first buffer body 254 and has a cover face256 that mates to the first buffer body 254. The first filament buffer250 has a bottom face 257 that mates to the second buffer body 255.

Each buffer body 254, 255 includes a cavity defined by a first side wall258, a second side wall 260, and a bottom wall 262 formed therein. Whenthe cover 252 is attached to the first buffer body 254, the firstsidewall 258, the second side wall 260, and the bottom wall 262 of thefirst buffer body 254 and the cover face 256 of the cover 252 define afirst buffer volume 264. When the first filament buffer 250 is stackedonto the second filament buffer 251, the first sidewall 258, the secondside wall 260, and the bottom wall 262 of the second buffer body 255 andthe bottom face 257 of the first buffer body 254 define a second buffervolume 265. The first and second buffer volumes 264, 265 allow thefilament 226 passing through the first and second filament buffers 250,251 to deflect. Deflection of the filament 226 within the filamentbuffers 264, 265 creates slack in the length of filament 226 between thefilament cartridges 240, 241 and the print head 214.

Each of the first and second filament buffers 250, 251 includes a firstopening 266 formed at a first distal end 268 and a second opening 270formed at a second distal end 272. The filament 226 from the firstfilament cartridge 240 enters the first filament buffer 250 through thefirst opening 266 of the first filament buffer 250 and exits through thesecond opening 270 of the first filament buffer 250. The filament 226from the second filament cartridge 241 enters the second filament buffer251 through the first opening 266 of the second filament buffer 251 andexits through the second opening 270 of the second filament buffer 251.The first buffer volume 264 is positioned between the first and secondopenings 266, 270 of the first filament buffer 250. The second buffervolume 265 is positioned between the first and second openings 266, 270of the second filament buffer 251.

Within each of the first and second buffer volumes 264, 265, the firstside wall 258 extends substantially linearly between the first andsecond openings 266, 270. The second side wall 260 extends between thefirst and second openings 266, 270 and includes a concave curved shapethat allows the filament 226 to deflect in the direction of the secondside wall 260 away from the first side wall 258. As the filament 226extends through the buffer volumes 264, 265 the filament 226 deflectstwo-dimensionally between a first position 274 and a second position276. In the first position 274, the filament 226 extends along asubstantially linear path between the first and second openings 266, 270adjacent the first side wall 258. In the second position 276, thefilament 226 extends along a curved path between the first and secondopenings 266, 270 adjacent the second side wall 260.

When the filament 226 deflects to the second position 274, there isslack in the filament 226, adding to the length of filament 226 withinthe buffer volumes 264, 265. The distance traveled by the filament 226between the first and second openings 266, 270 when the filament 226 isadjacent the first side wall 258 is shorter than the distance travelledby the filament 226 between the first and second openings 266, 270 whenthe filament 226 is adjacent the second side wall 260. When the extruder220 within the print head 214 pulls the filament 226 into the print head214, the extruder 220 must pull with enough force to overcome thefrictional resistance on the filament 226 upstream of the extruder 220.This can be particularly problematic if the spools 38 of coiled filamentare very large. The extruder 220 within the print head 214 must pullwith enough force to rotate the spools 238 and un-wind the filament 226from the coils. If the force is too much, the extruder 220 may not beable to pull with enough force to overcome the frictional resistance onthe filament 226. If this happens, the machine 210 will stopfunctioning. Alternatively, if the resistance is too much, the printhead feed motor 224 within the extruder 220 may strip the surface of thefilament 226 causing slippage in the extruder 220. Either instanceresults in a disruption in the operation of the machine 210.

Within each of filament buffers 250, 251, if the filament 226 isdeflected away from the first side wall 258 toward the second position276 within the buffer volume 264, 265, there is slack in the filament226 within the buffer volume 264, 265. This slack provides a free lengthof filament 226 within the buffer volume 264, 265 that can be pulledfrom the buffer volume 264, 265 with little resistance. When thefilament 226 is deflected away from the first side wall 258 and there isslack in the filament 226 within the buffer volume 264, 265, the forcenecessary to pull the filament 226 into the extruder 220 within theprint head 214 is not affected by any frictional resistance applied tothe filament 226 up-stream of the buffer volume 264, 265.

A first feed motor 278 is mounted within and integral to the firstfilament buffer 250. A second feed motor 279 is mounted within andintegral to the second filament buffer 251. The buffer body 254, 255 ofeach filament buffer 250, 251 includes a cavity 280 within which thefirst and second feed motors 278, 279 are positioned, and the cover 252is formed to provide a housing 282 for the first and second feed motors278, 279.

The first feed motor 278 pulls the filament 226 from the first filamentcartridge 240 and into the first opening 266 of the first filamentbuffer 250 and pushes the filament 226 into the first buffer volume 264.The second feed motor 279 pulls the filament 226 from the secondfilament cartridge 241 and into the first opening 266 of the secondfilament buffer 251 and pushes the filament 226 into the second buffervolume 265. The feed motors 278, 279 pull the filament from the filamentcartridges 240, 241 and push the filament 226 into the buffer volumes264, 265 faster than the extruder 220 pulls the filament 226 from thefirst and second filament buffers 250, 251. Because the filament 226 iscoming into the buffer volume 264, 265 faster than the filament 226 isexiting the buffer volume 264, 265, the filament 226 is forced todeflect within the buffer volume 264, 265.

The buffer body 254, 255 of each of the first and second filamentbuffers 250, 251 includes two sensor pockets 284, 286. A first sensorpocket 284 is formed within the first side wall 258 of each buffervolume 264, 265. A second sensor pocket 286 is formed within the secondside wall 260 of each buffer volume 264, 265. The sensor pockets 284,286 are adapted to support a sensor 288, 290 to detect the presence ofthe filament 226. A first sensor 288 is supported within the firstsensor pocket 284 within each buffer body 254, 255. A second sensor 290is supported within the second sensor pocket 286 within each buffer body254, 255. The sensors 288, 290 can be mechanical, wherein each sensor288, 290 includes a mechanical switch 292 extending into the buffervolume 264, 265 that is triggered when the filament 226 comes intophysical contact with the mechanical switch 292. Alternatively, thesensors 288, 290 can be optical sensors that are triggered when thefilament 226 is near the sensor 288, 290.

The sensors 288 provide feedback to allow proper control of the machine210. The machine 210 runs optimally when the filament 226 extendingthrough the first and second filament buffers 250, 251 is deflectedwithin the first and second buffer volumes 264, 265. Deflection isaccomplished due to the feed motors 278, 279 pushing the filament 226into the buffer volumes 264, 265 faster than the filament 226 is beingpulled from the filament buffers 250, 251. The sensors 288, 290 detectthe presence of the filament 226 within the buffer volumes 264, 265 andprovide that information to the controls of the machine 210.

When the filament 226 is being pulled from the first filament cartridge240, and is not deflected within the first buffer volume 264, the firstsensor 288 will detect the filament 226 adjacent the first side wall258. If the first sensor 288 detects the presence of the filament 226,the first feed motor 278 is turned on. The first feed motor 278 feedsfilament 226 into the first buffer volume 264 faster than the filament226 is being pulled from the first buffer volume 264 causing thefilament 226 to deflect. When the filament 226 has fully deflectedwithin the first buffer volume 264, the filament 226 will trigger thesecond sensor 290. When the second sensor 290 is triggered, the firstfeed motor 278 is turned off. As the machine 210 continues to operate,the extruder 220 in the print head 214 pulls filament 226 from the firstfilament buffer 250, taking up the slack in the filament 226 and causingless deflection of the filament 226. When all slack in the filament 226is gone, the filament 226 is no longer deflected and is adjacent thefirst side wall 258. When the first sensor 288 once again detects thatthe filament 226 is adjacent the first side wall 258, the first feedmotor 278 is once again turned on. This cycle is repeated as the machine210 operates. With feedback from the first and second sensors 288, 290within the first buffer body 254, the first feed motor 278 cycles on andoff as necessary to maintain deflection of the filament 226 within thefirst buffer volume 264 whenever the filament 226 is being pulled fromthe first filament buffer 250.

When the filament 226 is being pulled from the second filament cartridge241, and is not deflected within the second buffer volume 265, the firstsensor 288 will detect the filament adjacent the first side wall 258. Ifthe first sensor 288 within the second buffer body 255 detects thepresence of the filament 226, the second feed motor 279 is turned on.The second feed motor 279 feeds filament 226 into the second buffervolume 265 faster than the filament 226 is being pulled from the secondbuffer volume 265 causing the filament to deflect. When the filament 226has fully deflected within the second buffer volume 265, the filament226 will trigger the second sensor 290 within the second buffer body255. When the second sensor 290 is triggered, the second feed motor 279is turned off. As the machine 210 continues to operate, the extruder 220in the print head 214 pulls filament 226 from the second filament buffer251, taking up the slack in the filament 226 and causing less deflectionof the filament 226. When all slack in the filament 226 is gone, thefilament 226 is no longer deflected and is adjacent the first side wall258. When the first sensor 288 once again detects that the filament 226is adjacent the first side wall 258, the second feed motor 279 is onceagain turned on. This cycle is repeated as the machine 210 operates.With feedback from the first and second sensors 288, 290 within thesecond buffer body 255, the second feed motor 279 cycles on and off asnecessary to maintain deflection of the filament 226 within the secondbuffer volume 265 whenever the filament 226 is being pulled from thesecond filament buffer 251.

A filament intersection 294 is positioned between the first and secondfilament buffers 250, 251 and the print head 214. The first feed motor278 pulls filament 226 from the first filament cartridge 240 and feedsthe filament 226 through the first filament buffer 250 to the filamentintersection 294. The second feed motor 279 pulls filament 226 from thesecond filament cartridge 241 and feeds the filament 226 through thesecond filament buffer 251 to the filament intersection 294. FIG. 10C isa schematic representation of the path the filament 226 takes throughthe machine 210.

The filament intersection 294 is adapted to alternatively allow filament226 from the first and second filament buffers 250, 251 to be fed to theprint head 214. Filament 226 can only be fed to the print head 214 fromone of the filament buffers 250, 251. The filament intersection 294allows the filament 226 to be pulled from one of either the firstfilament buffer 250 or the second filament buffer 251. This provides theability to have more filament readily available to the machine 210. Whenthe filament 226 from the first filament cartridge 240 runs out, thefilament intersection 294 can switch over to pull filament from thesecond filament buffer 251 and second filament cartridge 241 withminimal interruption to the machine 210.

The description of the present disclosure is merely exemplary in natureand variations that do not depart from the gist of the presentdisclosure are intended to be within the scope of the presentdisclosure. Such variations are not to be regarded as a departure fromthe spirit and scope of the present disclosure.

What is claimed is:
 1. A machine for manufacturing additive printedparts, comprising: a first filament cartridge adapted to support alength of filament of a material from which the additive printed partswill be manufactured, a print head moveably supported within themachine; and a first filament buffer positioned between the firstfilament cartridge and the print head and including a first buffervolume, a first opening and a second opening; the first buffer volumepositioned between the first and second openings of the first filamentbuffer and including a first sidewall and a second side wall; the firstside wall extending substantially linearly between the first and secondopenings and the second side wall extending between the first and secondopenings and including a concave curved shape; wherein, the filamentsupported within the first filament cartridge extends from the firstfilament cartridge, into the first filament buffer through the firstopening, through the first filament buffer, out from the first filamentbuffer through the second opening, and to the print head, the firstbuffer volume adapted to allow the filament passing through the firstfilament buffer to deflect two-dimensionally toward the second side wallaway from the first side wall between a first position, wherein thefilament extends along a substantially linear path between the first andsecond openings adjacent the first side wall, and a second position,wherein the filament extends along a curved path between the first andsecond openings adjacent the second side wall.
 2. The machine of claim1, wherein the print head includes an extruder and a nozzle, theextruder adapted to pull the filament from the first filament bufferinto the print head and feed the filament into the nozzle.
 3. Themachine of claim 2, further including a first feed motor mounted withinand integral to the first filament buffer and positioned between thefirst filament cartridge and the first buffer volume, wherein the firstfeed motor is adapted to pull the filament from the first filamentcartridge and feed it into the first buffer volume.
 4. The machine ofclaim 3, wherein the distance traveled by the filament between the firstand second openings when the filament is adjacent the first side wall isshorter than the distance travelled by the filament between the firstand second openings when the filament is adjacent the second side wall,wherein when the filament is deflected toward the second side wall thereis slack in the filament within the buffer volume such that the forcenecessary to pull the filament into the print head by the extruder isnot affected by any resistance applied to the filament up-stream of thebuffer volume.
 5. The machine of claim 4, further comprising a firstsensor and a second sensor mounted within the first filament buffer, thefirst sensor adapted to detect the presence of the filament within thefirst buffer volume when the filament is positioned adjacent the firstside wall within the first buffer volume and the second sensor adaptedto detect the presence of the filament within the first buffer volumewhen the filament is positioned adjacent the second side wall within thefirst buffer volume.
 6. The machine of claim 5, further including aspool rotatably mounted within the first filament cartridge, the spooladapted to support a coiled length of filament and to rotate freely toallow filament to un-wind from the coil and to be pulled from the firstfilament cartridge.
 7. The machine of claim 6 further comprising asecond filament cartridge, substantially identical to the first filamentcartridge and adapted to support a length of the filament, a second feedmotor mounted within and integral to the first filament buffer andpositioned between the second filament cartridge and the first buffervolume, and a filament intersection positioned between the first andsecond feed motors and the first buffer volume of the first filamentbuffer, wherein the filament intersection is adapted to direct thefilament extending, alternatively, from either the first or secondfilament cartridges into the first buffer volume of the first filamentbuffer.
 8. The machine of claim 6, further comprising a second filamentcartridge, substantially identical to the first filament cartridge andadapted to support a length of the filament, and a second filamentbuffer positioned between the second filament cartridge and the printhead and having a second buffer volume; wherein the filament supportedwithin the second filament cartridge extends from the second filamentcartridge, through the second filament buffer, and to the print head,and the second buffer volumes is adapted to allow the filament passingthrough the second filament buffer to deflect.
 9. The machine of claim8, further including a second feed motor mounted within and integral tothe second filament buffer and positioned between the second filamentcartridge and the second buffer volume, wherein the filament supportedwithin the second filament cartridge is pulled from the second filamentcartridge and is fed into the second buffer volume by the second feedmotor.
 10. The machine of claim 9, wherein the second filament bufferincludes a first opening and a second opening, wherein the filamentextending from the second filament cartridge enters the second filamentbuffer through the first opening of the second filament buffer and exitsthe second filament buffer through the second opening of the secondfilament buffer.
 11. The machine of claim 10, further comprising afilament intersection positioned between the first and second filamentbuffers and the print head, wherein the filament intersection is adaptedto direct the filament extending, alternatively, from either the firstor second filament buffers to the print head.
 12. The machine of claim11, wherein the second buffer volume is positioned between the first andsecond openings of the second filament buffer and includes a firstsidewall and a second side wall, wherein the filament passing throughthe second buffer volume can deflect two-dimensionally between the firstand second side walls of the second buffer volume.
 13. The machine ofclaim 12, wherein the first side wall of the second buffer volumeextends substantially linearly between the first and second openings ofthe second filament buffer and the second side wall of the second buffervolume extends between the first and second openings of the secondfilament buffer and is shaped to allow the filament to deflecttwo-dimensionally between a first position, wherein the filament extendsalong a substantially linear path between the first and second openingsof the second filament buffer adjacent the first side wall of the secondbuffer volume, and a second position, wherein the filament extends alonga curved path between the first and second openings of the secondfilament buffer adjacent the second side wall of the second buffervolume.
 14. The machine of claim 13, wherein the distance traveled bythe filament between the first and second openings of the secondfilament buffer when the filament is adjacent the first side wall of thesecond buffer volume is shorter than the distance travelled by thefilament between the first and second openings of the second filamentbuffer when the filament is adjacent the second side wall of the secondbuffer volume, wherein when the filament is deflected toward the secondside wall of the second buffer volume there is slack in the filamentwithin the second buffer volume such that the force necessary to pullthe filament into the print head by the extruder is not affected by anyresistance applied to the filament up-stream of the second buffervolume.
 15. The machine of claim 14, further comprising a first sensorand a second sensor mounted within the second filament buffer to detectthe presence of the filament within the second buffer volume when thefilament is positioned adjacent the first side wall within the secondbuffer volume and the second sensor is adapted to detect the presence ofthe filament within the second buffer volume when the filament ispositioned adjacent the second side wall within the second buffervolume.
 16. The machine of claim 15, further comprising a spoolrotatably mounted within the second filament cartridge and adapted tosupport a coiled length of the filament and to rotate freely to allowfilament to un-wind from the coil and to be pulled from the secondfilament cartridge.